Unfortunately, you cannot flat tow the Tesla Model 3 or any other Tesla model behind an RV. Moreover, no electric car can be flat towed due to how the motors work. Essentially, the electric motors don’t allow the transmission or transfer case to be shifted into neutral, which is the only way that you can flat tow a vehicle.
If you want to take your Tesla with you wherever you go, the only surefire way to get it to your destination is by buying a flatbed trailer. However, these trailers can cost between $1,000 and $3,000, so you may need to budget.